Thin Film Comprising Titanium Oxide as Main Component and Sintered Compact Sputtering Target Comprising Titanium Oxide as Main Component

ABSTRACT

A thin film comprising titanium oxide as its main component includes titanium, oxygen and copper, content of Ti is 29.0 to 34.0 at % and content of Cu is 0.003 to 7.7 at % or less with remainder being oxygen and unavoidable impurities. A ratio of oxygen component to metal components, O/(2Ti+0.5Cu), is 0.96 or higher. The thin film has a high refractive index and low extinction coefficient. A sintered compact sputtering target suitable for producing the foregoing thin film is also provided and can be used to obtain a thin film with superior transmittance and low reflectance and which is effective as an interference film or protective film of an optical information recording medium, and to obtain a thin film that can be applied to a glass substrate; that is, a thin film that can be used as a heat ray reflective film, antireflection film, and interference filter.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. Application No.13/145,641 which is the National Stage of International Application No.PCT/JP2010/051232, filed Jan. 29, 2010, which claims the benefit under35 USC 119 of Japanese Application No. 2009-025064, filed Feb. 5, 2009,and Japanese Application No. 2009-089653, filed Apr. 2, 2009.

BACKGROUND

The present invention relates to a thin film comprising titanium oxideas its main component with a high refractive index and low extinctioncoefficient and a sintered compact sputtering target comprising titaniumoxide as its main component which is suitable for producing theforegoing thin film.

In recent years, technology of high density recording optical disks,which are high density optical information recording mediums capable ofrewriting without using a magnetic head, has been developed, and theseoptical disks are being commercialized at a rapid rate. In particular,ever since its appearance in 1977 as a rewritable CD, CD-RW is the mostpopular phase-change optical disk. The rewrite cycle of a CD-RW isapproximately 1000 times. Moreover, DVD-RW for use as a DVD has beendeveloped and commercialized, and the layer structure of this disk isbasically the same as or similar to a CD-RW. The rewrite cycle of aDVD-RW is approximately 1000 to 10000 times. These are electronic partsthat record, reproduce and rewrite information by irradiating a laserbeam and optically changing the transmittance, reflectance and the likeof the recording material, and have spread rapidly.

Generally speaking, a phase-change optical disk used as a CD-RW, aDVD-RW or the like has a four-layer structure in which both sides of arecording thin film layer based on Ag—In—Sb—Te, Ge—Sb—Te or the likewith a high melting point dielectric protective layer made of ZnS, SiO₂or the like, and which is additionally provided with a silver or silveralloy or aluminum alloy reflective film. Moreover, in order to increasethe rewrite cycle, an interface layer is added between a memory layerand a protective layer as needed. A reflective layer and a protectivelayer are demanded of optical functions of increasing the difference ofreflectance between the amorphous part and crystal part of the recordinglayer, and additionally demanded of humidity resistance of the recordingthin film and a function for preventing deformation caused by heat, anda function of controlling the thermal conditions upon recording (referto Technical Journal “Kogaku” Volume 26, Issue 1, Pages 9-15).

Recently, a single-sided, dual layer optical recording medium has beenproposed to realize larger capacity and higher density (refer toJapanese Published Unexamined Patent Application No. 2006-79710). In JP2006-79710, there is a first information layer formed on a substrate 1and a second information layer formed on a substrate 2 from the incidentdirection of the laser beam, and these layers are affixed to each otherwith an intermediate layer interposed therebetween so that theinformation films face each other. In the foregoing case, the firstinformation layer is configured from a recording layer and a first metalreflective layer, and the second information layer is configured from afirst protective layer, a second protective layer, a recording layer,and a second metal reflective layer. In addition, layers such as a hardcoat layer and a thermal diffusion layer may be arbitrarily formed forprotection against scratches, contamination and the like. Moreover,various materials have been proposed as the protective layer, recordinglayer, reflective layer and other layers.

A high melting point dielectric protective layer requires toleranceagainst repeated thermal stress by warming and cooling, requires thethermal effect not to affect the reflective film or other locations,needs to be thin with low reflectance, and requires strength that isfree from deterioration. In this respect, the dielectric protectivelayer plays an important role. The recording layer, reflective layer,interference film layer and the like are similarly important in thatthey exhibit their functions respectively in the foregoing electronicparts such as CDs and DVDs.

The respective thin films with the foregoing multilayer structure arenormally formed with the sputtering method. The principal of thesputtering method is as follows; specifically, the sputtering methodcauses a substrate and a target as a positive electrode and a negativeelectrode to face each other, and applies a high voltage between thesubstrate and the target under an inert gas atmosphere in order togenerate an electric field. Here, the ionized electrons and inert gascollide and form plasma, the positive ions in the plasma collide withthe target (negative electrode) surface and sputter the atomsconfiguring the target, and the sputtered atoms adhere to the opposingsubstrate surface so as to form a film.

In the foregoing circumstances, a target using titanium oxide (TiO_(x))has been proposed as a sputtering target for forming a heat rayreflective film and an antireflection film (refer to Japanese Patent No.3836163). Here, the specific resistance value is set to 0.35 Ωcm or lessto stabilize the discharge during sputtering. Consequently, DCsputtering is enabled and a film with a high refractive index can beobtained. Here, the transmittance of the film will deteriorate, so theoxygen content is set to be 35 wt % or higher, and measures forintroducing oxygen are additionally adopted. And, since the depositionrate will deteriorate due to the introduction of oxygen, a metal oxideis added to improve the deposition rate. However, there are problems inapplying the target of Japanese Patent No. 3836163 to precision opticalmembers and electronic parts that require films with a high refractiveindex and low absorption. Particularly on the short-wave length side inthe vicinity of 400 nm is considered problematic.

SUMMARY

In light of the foregoing problems, an object of this invention is toprovide a thin film comprising titanium oxide as its main component witha high refractive index and low extinction coefficient and a sinteredcompact sputtering target comprising titanium oxide as its maincomponent which is suitable for producing the foregoing thin film, andsimultaneously provide a thin film with superior transmittance and lowreflectance and which is effective as an interference film or protectivefilm of an optical information recording medium. Moreover, the thin filmof the present invention can also be applied to a glass substrate; thatis, the thin film that can also be used as a heat ray reflective film,antireflection film, and interference filter.

In order to achieve the foregoing object, as a result of intense study,the present inventors discovered that the addition of metal such ascopper and platinum to titanium oxide is extremely effective in order toobtain a material capable of maintaining transmittance and preventingdeterioration of reflectance without impairing the characteristics of aninterference film or a protective film of an optical informationrecording medium.

Based on the foregoing discovery, the present invention provides a thinfilm comprising titanium oxide as its main component, wherein the thinfilm includes titanium, oxygen and copper, content of Ti is 29.0 at % orhigher and 34.0 at % or less and content of Cu is 0.003 at % or higherand 7.7 at % or less with remainder being oxygen and unavoidableimpurities, and ratio of oxygen component to metal components,O/(2Ti+0.5Cu), is 0.96 or higher. The present invention also provides athin film comprising titanium oxide as its main component, wherein thethin film includes titanium, oxygen and platinum, content of Ti is 29.0at % or higher and 34.0 at % or less and content of Pt is 0.003 at % orhigher and 5.7 at % or less with remainder being oxygen and unavoidableimpurities, and ratio of oxygen component to metal components,O/(2Ti+Pt), is 0.95 or higher. Still further, the present inventionprovides a thin film comprising titanium oxide as its main component,wherein the thin film includes titanium, oxygen and one or more types ofmetal M selected from cobalt, nickel, palladium and gold, content of Tiis 29.0 at % or higher and 34.0 at % or less and content of M is 0.003at % or higher and 7.7 at % or less with remainder being oxygen andunavoidable impurities, and ratio of oxygen component to metalcomponents, O/(2Ti+M), is 0.95 or higher. The thin films comprisingtitanium oxide as its main component may have a refractive index in awavelength region of 400 to 410 nm of 2.60 or higher and may have anextinction coefficient in the wavelength region of 400 to 410 nm of 0.1or less or of 0.05 or less. The thin film may be an optical interferencefilm or a protective film, or the thin film may be an optical recordingmedium.

The present invention additionally provides a sintered compactsputtering target comprising titanium oxide as its main component,wherein the target includes copper and comprises, as its main component,titanium oxide made of titanium, oxygen and unavoidable impurities as aremainder thereof, the respective components have a composition ratio of(TiO_(2-m))_(1-n)Cu_(n) (provided that 0≦m≦0.5 and 0.0001≦n≦0.2), andthe target has a specific resistance of 100 Ωcm or less. In addition,the present invention provides a sintered compact sputtering targetcomprising titanium oxide as its main component, wherein the targetincludes platinum and comprises, as its main component, titanium oxidemade of titanium, oxygen and unavoidable impurities as a remainderthereof, the respective components have a composition ratio of(TiO_(2-m))_(1-n)Pt_(n) (provided that 0≦m≦0.5 and 0.0001≦n≦0.15), andthe target has a specific resistance of 100 Ωcm or less. Still further,the present invention provides a sintered compact sputtering targetcomprising titanium oxide as its main component, wherein the targetincludes one or more types of metal M selected from cobalt, nickel,palladium and gold and comprises, as its main component, titanium oxidemade of titanium, oxygen and unavoidable impurities as a remainderthereof, the respective components have a composition ratio of(TiO_(2-m))_(1-n)M_(n) (provided that 0≦m≦0.5 and 0.0001≦n≦0.2), and thetarget has a specific resistance of 100 Ωcm or less.

As described above, the present invention provides a thin filmcomprising titanium oxide as its main component with a high refractiveindex and low extinction coefficient and a sintered compact sputteringtarget comprising titanium oxide as its main component which is suitablefor producing the foregoing thin film, and the thin film obtained withthe present invention yields a significant effect as a film or layer ofan optical information recording medium. Moreover, the thin film of thepresent invention simultaneously yields superior transmittance and lowreflectance and is particularly effective as an interference film orprotective film of an optical information recording medium. A highmelting point dielectric protective layer requires tolerance againstrepeated thermal stress by warming and cooling, and the foregoingthermal effect must not affect the reflective film or other locations,needs to be thin with low reflectance, and requires strength that isfree from deterioration. The thin film comprising titanium oxide as itsmain component of the present invention comprises characteristics thatcan be applied to this kind of material. Moreover, since the oxygenamount during sputtering can be adjusted within a small range, there isan additional effect of being able to inhibit the deterioration of thedeposition rate.

DETAILED DESCRIPTION

As described above, the thin film comprising titanium oxide as its maincomponent according to the present invention includes, in addition totitanium and O components, copper or platinum or one or more types ofmetal M selected from cobalt, nickel, palladium and gold. In the case ofincluding copper, the thin film comprising titanium oxide as its maincomponent has a composition ratio where content of Ti is 29.0 at % orhigher and 34.0 at % or less and content of Cu is 0.003 at % or higherand 7.7 at % or less with remainder being oxygen and unavoidableimpurities, and ratio of oxygen component to metal components,O/(2Ti+0.5 Cu), is 0.96 or higher. Moreover, in the case of includingplatinum, the thin film comprising titanium oxide as its main componenthas a composition ratio where content of Ti is 29.0 at % or higher and34.0 at % or less and content of Pt is 0.003 at % or higher and 5.7 at %or less with remainder being oxygen and unavoidable impurities, andratio of oxygen component to metal components, O/(2Ti+Pt), is 0.95 orhigher. Furthermore, in the case of including one or more types of metalM selected from cobalt, nickel, palladium and gold, the thin filmcomprising titanium oxide as its main component has a composition ratiowhere content of Ti is 29.0 at % or higher and 34.0 at % or less andcontent of M is 0.003 at % or higher and 7.7 at % or less with remainderbeing oxygen and unavoidable impurities, and ratio of oxygen componentto metal components, O/(2Ti+M), is 0.95 or higher.

The existence of copper or platinum or one or more types of metal Mselected from cobalt, nickel, palladium and gold yields the effect ofincreasing the refractive index of the thin film. If the content is lessthan 0.003, the addition effect is small, and if the content exceeds 7.7at % (cases of adding copper or one or more types of metal M selectedfrom cobalt, nickel, palladium and gold) or 5.7 at % (case of addingplatinum), the extinction coefficient of the thin film tends toincrease. Thus, it could be said that the abundance of copper orplatinum or one or more types of metal M in the thin film is preferably0.003 at % or higher and 7.7 at % or less (5.7 at % or less in thelatter case).

Although the reason that the refractive index increases is notnecessarily clear, the cause is considered to be because copper orplatinum or one or more types of metal M selected from cobalt, nickel,palladium and gold are dispersed as fine particles (nano particles, forinstance) in the titanium oxide amorphous film. In certain cases, a partof these added metals exist as metal oxide, but even in cases where theypartially exist as an oxide, there is no particular problem, and theimprovement in the refractive index is similarly acknowledged. Thematerial with a high refractive index obtained as described above is aneven more favorable material since the freedom of designing a multilayeroptical film can be improved.

These thin films are amorphous films, and it is possible to obtain afilm with a refractive index of 2.60 or higher in a wavelength region of400 to 410 nm. Moreover, it is also possible to obtain a thin film withan extinction coefficient of 0.1 or less, and even a thin film with anextinction coefficient of 0.05 or less in a wavelength region of 400 to410. The foregoing wavelength range of 400 to 410 nm is that of a bluelaser, and the refractive index is 2.60 or higher in this wavelengthrange as described above, but higher the refractive index, the better itis. Moreover, although it is possible to achieve an extinctioncoefficient of 0.1 or less, and even 0.05 or less, the lower theextinction coefficient, the more suitable it is for multi-layering. Thisthin film comprising titanium oxide as its main component is effectiveas an interference film or a protective film, and is particularlyeffective as an optical recording medium.

The foregoing thin film can be produced by using a sintered compactsputtering target comprising titanium oxide as its main component,wherein the target includes copper or one or more types of metal Mselected from cobalt, nickel, palladium and gold and comprises, as itsmain component, titanium oxide made of titanium, oxygen and unavoidableimpurities as a remainder thereof, the respective components have acomposition ratio of (TiO_(2-m))_(1-n)Cu_(n) (provided that 0≦m≦0.5 and0.0001≦n≦0.2), and the target has a specific resistance of 100 Ωcm orless. The foregoing thin film can also be produced by using a sinteredcompact sputtering target comprising titanium oxide as its maincomponent, wherein the target includes platinum and comprises, as itsmain component, titanium oxide made of titanium, oxygen and unavoidableimpurities as a remainder thereof, the respective components have acomposition ratio of (TiO_(2-n))_(1-n)Pt_(n) (provided that 0≦m≦0.5 and0.0001≦n≦0.15), and the target has a specific resistance of 100 Ωcm orless.

With the sputtering in the foregoing case, it is possible to obtain athin film comprising titanium oxide as its main component with a lowextinction coefficient by making adjustments so that oxygen isintroduced in the sputtering gas especially in cases where the amount ofadded metal is large. The sintered compact target of the presentinvention has a similar component composition as the thin film, but notthe same. Specifically, the basic components of the target include Ti,added metal (Cu, Pt, Co, Ni, Pd and Au), and O component, and therespective components have the foregoing composition ratio. Moreover,this target comprises a specific resistance of 100 Ωcm or less.

In the foregoing case, m is preferably 0.5 or less for this reason: if mexceeds 0.5, the oxygen deficiency increases excessively and theextinction coefficient tends to increase. Moreover, n is preferably0.0001 or higher and 0.2 (provided that this is 0.15 in the case of Pt)or less for this reason: if n is less than 0.001, the addition effect ofCu, Pt, Co, Ni, Pd, Au is small, and if n exceeds 0.2 (provided thatthis is 0.15 in the case of Pt), the extinction coefficient tends toincrease in the foregoing deposition. The conductivity of the target isrequired in order to increase the sputtering efficiency, and the targetof the present invention comprises these conditions and can be subjectto DC sputtering. Since the Cu, Pt, Co, Ni, Pd, Au phases existing inthe sintered compact sputtering target are able to exhibit effects ofpreventing an abnormal discharge if they are uniformly dispersed as finegrains, it could be said that their average particle diameter ispreferably 20 μm or less. By using this sintered compact sputteringtarget and sputtering it in an argon gas atmosphere containing 0.1 to16% of oxygen, it is possible to form a titanium oxide thin filmcontaining Cu, Pt, Co, Ni, Pd, Au and/or the oxides of these metals on asubstrate.

Upon producing the thin film, a sintered compact sputtering targethaving the foregoing composition ratio and a specific resistance of 100Ωcm or less can be used and sputtered in an argon gas atmospherecontaining 0.1 to 16% of oxygen. Specifically, it is thereby possible toform a thin film comprising titanium oxide as its main component,wherein the thin film includes titanium, oxygen and copper, content ofTi is 29.0 at % or higher and 34.0 at % or less and content of Cu is0.003 at % or higher and 7.7 at % or less with remainder being oxygenand unavoidable impurities, and ratio of oxygen component to metalcomponents, O/(2Ti+0.5 Cu), is 0.96 or higher, or a thin film comprisingtitanium oxide as its main component, wherein the thin film includestitanium, oxygen and platinum, content of Ti is 29.0 at % or higher and34.0 at % or less and content of Pt is 0.003 at % or higher and 5.7 at %or less with remainder being oxygen and unavoidable impurities, andratio of oxygen component to metal components, O/(2 Ti+Pt), is 0.95 orhigher, or a thin film comprising titanium oxide as its main component,wherein the thin film includes titanium, oxygen and one or more types ofmetal M selected from cobalt, nickel, palladium and gold, content of Tiis 29.0 at % or higher and 34.0 at % or less and content of M is 0.003at % or higher and 7.7 at % or less with remainder being oxygen andunavoidable impurities, and ratio of oxygen component to metalcomponents, O/(2 Ti+M), is 0.95 or higher. Here, the thin film can beformed with DC sputtering.

Upon producing the target, as the raw material, preferably used is highpurity (normally 4N or higher) powder of titanium oxide (TiO₂) with anaverage particle diameter of 10 μm or less and high purity (normally 3Nor higher) powder of copper or platinum or one or more types of metal Mselected from cobalt, nickel, palladium and gold with an averageparticle diameter of 20 μm or less. These are blended to achieve thecomposition ratio of the present invention. Then, the added metals thatwere selected are mixed so as to be uniformly dispersed in the titaniumoxide powder using a wet ball mill or a dry blender (mixer).

After the mixing, the mixed powder is filled in a carbon die andsubsequently subject to hot press. The hot press conditions may bechanged depending on the composition component, but normally the hotpress is performed within a range of 800 to 1100° C. and bearing of 100to 500 kgf/cm². Nevertheless, these conditions are representativeconditions, and the selection thereof is arbitrarily and there is noparticular limitation. After sintering, the sintered compact is machinedand finished into a target shape. It is thereby possible to obtain atarget in which the basic components are titanium, copper or platinum orone or more types of metal M selected from cobalt, nickel, palladium andgold, and oxygen component. With this target, the respective componentshave the foregoing composition ratio, and copper or platinum or one ormore types of metal M selected from cobalt, nickel, palladium and goldand/or the oxides thereof are dispersed as fine particles in the matrixof the titanium oxide.

EXAMPLES

The present invention is now explained with reference to the Examplesand Comparative Examples. Note that these Examples are merelyillustrative, and the present invention shall in no way be limitedthereby. In other words, various modifications and other embodiments arecovered by the present invention, and the present invention is limitedonly by the scope of its claims.

Examples 1 to 8

As the raw materials, titanium oxide (TiO₂) with an average particlediameter of 3 μm and purity of 4N (99.99%), and copper powder with anaverage particle diameter of 15 μm and purity of 3N (99.9%) were used.These were blended and mixed to achieve the target compositions shown inTable 1. One kg of this mixed powder was mixed using a wet ball mill sothat copper is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried by vaporizing moisture wasfilled in a carbon die and hot pressed. The hot press conditions were970° C., and bearing of 200 kgf/cm². The obtained sintered compact wasmachined to obtain a target of φ152 mm and 5 mmt Consequently, targetswith density of 97% or higher and specific resistance of 0.01 to 10 Ωcmas shown in Table 1 were obtained. There was no abnormal dischargeduring the sputtering. The results are shown in Table 1.

TABLE 1 Film Composition Specific Deposition Composition of TargetResistance Sputter Speed Ti Cu O O/(2Ti + Refractive Extinction (at %)(Ωcm) gas (Å/sec/kW) (at %) (at %) (at %) 0.5Cu) index coefficientExample 1 TiO₂:Cu = 90:10 0.8 Ar—4%O₂ 0.7 32 3.5 64.5 0.98 2.65 0.02Example 2 TiO₂:Cu = 95:5 3 Ar—2%O₂ 1 32.8 1.7 65.5 0.99 2.64 0.01Example 3 TiO₂:Cu = 99:1 7 Ar—2%O₂ 0.9 33.1 0.4 66.5 1.00 2.62 0.007Example 4 TiO₂:Cu = 99:1 7 Ar 1.7 33.4 0.4 66.2 0.99 2.66 0.03 Example 5TiO₂:Cu = 99.99:0.1 10 Ar 1.6 33.3 0.04 66.66 1.00 2.62 0.006 Example 6TiO_(1.5):Cu = 99:1 0.01 Ar—10%O₂ 0.4 33.9 0.4 65.7 0.97 2.61 0.08Example 7 TiO₂:Cu = 80:20 0.03 Ar—10%O₂ 0.5 30.5 7.6 61.9 0.96 2.68 0.01Example 8 TiO_(1.5):Cu = 99.99:0.01 10 Ar 1.6 33.3 0.003 66.697 1.00 2.60.005 Comparative TiO₂ = 100 >100 Ar—2%O₂ 0.9 33.2 0 66.8 1.01 2.590.004 Example 1 Comparative TiO₂:Cu = 99:5 3 Ar 1.8 33.5 1.8 64.7 0.952.7 0.2 Example 2 Comparative TiO₂:Cu = 70:30 0.0005 Ar—10%O₂ 0.5 2912.3 58.7 0.92 2.61 0.2 Example 3 Comparative TiO₂:Cu = 99.995: 0.005 20Ar 1.6 33.3 0.002 66.698 1.00 2.59 0.005 Example 4 ComparativeTiO_(1.5):Cu = 99:1 0.01 Ar 1.5 39.5 0.4 60.1 0.76 2.55 0.5 Example 5

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. The sputtering conditionswere, as shown in Table 1: DC sputtering was performed in an Ar gasatmosphere or Ar gas-O₂ (2 to 10%) gas atmosphere and at a gas pressureof 0.5 Pa, gas flow rate of 50 sccm, and sputtering power of 500 to 1000w. Consequently, it was possible to perform DC sputtering without anyproblem, and it was confirmed that the target possesses conductivity. A1 μm sputtered film was formed on the glass substrate. In Table 1, thedeposition rate and composition of the film analyzed with EPMA (SIMS ina low Cu concentration region) are respectively shown. Amount of O isthe remainder of Ti and Cu. As Table 1 shows, O/(2Ti+0.5Cu) was 0.96 to1.00. The refractive index and extinction coefficient of the sputteredfilm were measured. They were measured with an ellipsometer using alight wavelength of 405 nm. The results are similarly shown in Table 1.Consequently, the refractive index was high at 2.6 to 2.68, and theextinction coefficient decreased at 0.005 to 0.08. In all cases it waspossible to form an interference film or a protective film suitable foran optical recording medium.

Comparative Examples 1 to 5

As the raw materials, titanium oxide (TiO₂) with an average particlediameter of 3 μm and purity of 4N (99.99%), and copper powder with anaverage particle diameter of 15 μm and purity of 3N (99.9%) were used.These were blended and mixed to achieve the target compositions shown inTable 1. Note that Comparative Example 1 shows a case of not addingcopper powder. One kg of this mixed powder was mixed using a wet ballmill so that copper is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried by vaporizing moisture wasfilled in a carbon die and hot pressed. The hot press conditions were970° C., and bearing of 200 kgf/cm². The obtained sintered compact wasmachined to obtain a target of φ152 mm and 5 mmt. Consequently, thedensity was 95 to 98%. As shown in Table 1, the specific resistance ofthe target was >100 Ωcm to 0.0005 Ωcm.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. The sputtering conditionswere, as shown in Table 1: DC sputtering was performed in an Ar gasatmosphere or Ar gas-O₂ (2 to 10%) gas atmosphere and at a gas pressureof 0.5 Pa, gas flow rate of 50 seem, and sputtering power of 500 to 1000w. A 1 μm sputtered film was formed on the glass substrate. Thedeposition rate and composition of the film analyzed with EPMA (SIMS ina low Cu concentration region) are respectively shown in Table 1. AsTable 1 shows, O/(2 Ti+0.5 Cu) was 0.76 to 1.00. The refractive indexand extinction coefficient of the sputtered film were measured. Theywere measured with an ellipsometer using a light wavelength of 405 nm.The results are similarly shown in Table 1.

Comparative Example 1 is a titanium oxide target to which Cu was notadded. Although the extinction coefficient was low at 0.004, therefractive index decreased to 2.59. Thus, it was inadequate as aninterference film or a protective film of an optical recording medium.Comparative Example 2 did not satisfy the conditions of the presentinvention since the ratio of oxygen component to metal components,O/(2Ti+0.5Cu) was 0.95. Here, although the refractive index was high at2.7, the extinction coefficient contrarily increased to 0.2. Thus, itwas inadequate as an interference film or a protective film of anoptical recording medium. Comparative Example 3 did not satisfy theconditions of the present invention since the Cu amount was too greatand the ratio of oxygen component to metal components, O/(2Ti+0.5Cu) was0.92. Here, although the refractive index was high at 2.7, theextinction coefficient contrarily increased to 0.2. Thus, it wasinadequate as an interference film or a protective film of an opticalrecording medium.

Comparative Example 4 did not satisfy the conditions of the presentinvention since the Cu amount was small at 0.002 at %. Here, althoughthe extinction coefficient decreased to 0.005, the refractive index wascontrarily low at 2.59. Thus, it was inadequate as an interference filmor a protective film of an optical recording medium. Comparative Example5 did not satisfy the conditions of the present invention since theratio of oxygen component to metal component, O/(2Ti+0.5Cu) was low at0.76. Here, the refractive index was low at 2.55, and the extinctioncoefficient also increased to 0.5. Thus, it was inadequate as aninterference film or a protective film of an optical recording medium.

Example 9 to Example 15

As the raw materials, titanium oxide (TiO₂) with an average particlediameter of 3 μm and purity of 4N (99.99%), and palladium (Pd) powderwith an average particle diameter of 25 μm and purity of 3N (99.9%) wereused. These were blended and mixed to achieve the target compositionsshown in Table 2. One kg of this mixed powder was mixed using a wet ballmill so that Pd is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried by vaporizing moisture wasfilled in a carbon die and hot pressed. The hot press conditions were970° C., and bearing of 200 kgf/cm². The obtained sintered compact wasmachined to obtain a target of φ152 mm and 5 mmt Consequently, targetswith density of 95% or higher and specific resistance of 0.01 to 30 Ωcmas shown in Table 2 were obtained.

TABLE 2 Film Composition Specific Deposition Composition of TargetResistance Sputter Speed Ti Pd O O/(2Ti + Refractive Extinction (at %)(Ωcm) gas (Å/sec/kW) (at %) (at %) (at %) Pd) index coefficient Example9 TiO₂:Pd = 90:10 9 Ar—4%O₂ 0.7 31.9 3.6 64.5 0.96 2.65 0.05 Example 10TiO₂:Pd = 95:5 20 Ar—2%O₂ 1.1 32.7 1.7 65.6 0.98 2.62 0.05 Example 11TiO₂:Pd = 99:1 30 Ar—2%O₂ 0.9 33.1 0.4 66.5 1.00 2.61 0.01 Example 12TiO₂:Pd = 99.9:0.1 6 Ar 1.6 33.2 0.04 66.76 1.00 2.60 0.008 Example 13TiO_(1.5):Pd = 95:5 0.01 Ar—10%O₂ 0.5 33 2.1 64.9 0.95 2.65 0.07 Example14 TiO₂:Pd = 80:20 0.3 Ar—10%O₂ 0.5 29.6 7.4 63 0.95 2.68 0.1 Example 15TiO_(1.9):Pd = 99.99:0.01 0.05 Ar—1%O₂ 1.3 33.3 0.004 66.696 1.00 2.650.009 Comparative TiO₂:Pd = 95:5 20 Ar 1.8 33.5 1.8 64.7 0.94 2.68 0.19Example 6 Comparative TiO₂:Pd = 70:30 0.001 Ar—20%O₂ 0.3 28.5 12.5 590.85 2.54 0.3 Example 7

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. The sputtering conditionswere, as shown in Table 2: DC sputtering was performed in an Ar gasatmosphere or Ar gas-O₂ (1 to 10%) gas atmosphere and at a gas pressureof 0.5 Pa, gas flow rate of 50 sccm, and sputtering power of 500 to 1000w. It was possible to perform DC sputtering without any problem, and itwas confirmed that the target possesses conductivity. A 1 μm sputteredfilm was formed on the glass substrate. The deposition rate andcomposition of the film analyzed with EPMA are respectively shown inTable 2. As Table 2 shows, O/(2Ti+Pd) was 0.95 to 1.00. The refractiveindex and extinction coefficient of the sputtered film were measured.They were measured with an ellipsometer using a light wavelength of 405nm. The results are similarly shown in Table 2. Consequently, therefractive index was high at 2.60 to 2.68, and the extinctioncoefficient decreased at 0.008 to 0.1. In all cases, it was possible toform an interference film or a protective film suitable for an opticalrecording medium.

Comparative Example 6 and Comparative Example 7

As the raw materials, titanium oxide (TiO₂) with an average particlediameter of 3 μm and purity of 4N (99.99%), and palladium (Pd) powderwith an average particle diameter of 25 μm and purity of 3N (99.9%) wereused. These were blended and mixed to achieve the target compositionsshown in Table 2. One kg of this mixed powder was mixed using a wet ballmill so that Pd is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried by vaporizing moisture wasfilled in a carbon die and hot pressed. The hot press conditions were970° C., and bearing of 200 kgf/cm². The obtained sintered compact wasmachined to obtain a target of φ152 mm and 5 mmt Consequently, thedensity was 95% or higher. As shown in Table 2, the specific resistanceof the target was 0.001 Ωcm to 20 Ωcm.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. The sputtering conditionswere, as shown in Table 2: DC sputtering was performed in an Ar gasatmosphere or Ar gas-O₂ (20%) gas atmosphere and at a gas pressure of0.5 Pa, gas flow rate of 50 sccm, and sputtering power of 500 to 1000 w.A 1 μm sputtered film was formed on the glass substrate. The depositionrate and composition of the film analyzed with EPMA are respectivelyshown in Table 2. As Table 2 shows, O/(2Ti+Pd) was 0.85 to 0.94. Therefractive index and extinction coefficient of the sputtered film weremeasured. They were measured with an ellipsometer using a lightwavelength of 405 nm. The results are similarly shown in Table 2.

As a result of the above, Comparative Example 6 did not satisfy theconditions of the present invention since the ratio of oxygen componentto metal components, O/(2 Ti+Pd) was 0.94. Here, although the refractiveindex was high at 2.68, the extinction coefficient contrarily increasedto 0.19. Thus, it was inadequate as an interference film or a protectivefilm of an optical recording medium. Comparative Example 7 did notsatisfy the conditions of the present invention since the Pd amount wastoo great at 12.5 at % and the ratio of oxygen component to metalcomponents, O/(2Ti+Pd) was 0.85. Here, the refractive index was low at2.54, and the extinction coefficient increased to 0.3. Thus, it wasinadequate as an interference film or a protective film of an opticalrecording medium.

Example 16 to Example 21

As the raw materials, titanium oxide (TiO₂) with an average particlediameter of 3 μm and purity of 4N (99.99%), and cobalt (Co) powder withan average particle diameter of 25 μm and purity of 3N (99.9%) wereused. These were blended and mixed to achieve the target compositionsshown in Table 3. One kg of this mixed powder was mixed using a wet ballmill so that Co is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried by vaporizing moisture wasfilled in a carbon die and hot pressed. The hot press conditions were970° C., and bearing of 300 kgf/cm². The obtained sintered compact wasmachined to obtain a target of φ152 mm and 5 mmt Consequently, targetswith density of 95% or higher and specific resistance of 0.06 to 50 Ωcmas shown in Table 3 were obtained.

TABLE 3 Film Composition Specific Deposition Composition of TargetResistance Sputter Speed Ti Co O O/(2Ti + Refractive Extinction (at %)(Ωcm) gas (Å/sec/kW) (at %) (at %) (at %) Co) index coefficient Example16 TiO₂:Co = 90:10 6 Ar—2%O₂ 1.1 31.9 3.6 64.5 0.96 2.63 0.05 Example 17TiO₂:Co = 95:5 15 Ar—2%O₂ 1 32.7 1.7 65.6 0.98 2.62 0.03 Example 18TiO₂:Co 99:1 28 Ar—2%O₂ 0.9 33.1 0.3 66.6 1.00 2.61 0.02 Example 19TiO₂:Co = 99.9:0.1 50 Ar 1.6 33.3 0.04 66.66 1.00 2.61 0.01 Example 20TiO₂:Co = 80:20 0.1 Ar—10%O₂ 0.5 29.6 7.3 63.1 0.95 2.67 0.1 Example 21TiO_(1.9):Co = 99.99:0.01 0.06 Ar—0.5%O₂ 1.4 33.5 0.003 66.497 0.99 2.650.01 Comparative TiO₂:Co = 90:10 6 Ar 1.8 32.2 3.7 64.1 0.94 2.57 0.11Example 8 Comparative TiO₂:Co = 70:30 0.002 Ar—20%O₂ 0.3 28.7 12.5 58.80.84 2.55 0.32 Example 9

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. The sputtering conditionswere, as shown in Table 3: DC sputtering was performed in an Ar gasatmosphere or Ar gas-O₂ (0.5 to 10%) gas atmosphere and at a gaspressure of 0.5 Pa, gas flow rate of 50 sccm, and sputtering power of500 to 1000 w. Thus, it was possible to perform DC sputtering withoutany problem, and it was confirmed that the target possessesconductivity. A 1 μm sputtered film was formed on the glass substrate.The deposition rate and composition of the film analyzed with EPMA arerespectively shown in Table 3. As Table 3 shows, O/(2Ti+Co) was 0.95 to1.00. The refractive index and extinction coefficient of the sputteredfilm were measured. They were measured with an ellipsometer using alight wavelength of 405 nm. The results are similarly shown in Table 3.Consequently, the refractive index was high at 2.61 to 2.67, and theextinction coefficient decreased at 0.01 to 0.1. In all cases it waspossible to form an interference film or a protective film suitable foran optical recording medium.

Comparative Example 8 and Comparative Example 9

As the raw materials, titanium oxide (TiO₂) with an average particlediameter of 3 μm and purity of 4N (99.99%), and cobalt (Co) powder withan average particle diameter of 20 μm and purity of 3N (99.9%) wereused. These were blended and mixed to achieve the target compositionsshown in Table 3. One kg of this mixed powder was mixed using a wet ballmill so that Co is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried by vaporizing moisture wasfilled in a carbon die and hot pressed. The hot press conditions were970° C., and bearing of 300 kgf/cm². The obtained sintered compact wasmachined to obtain a target of φ52 mm and 5 mmt Consequently, thedensity was 95% or higher. As shown in Table 3, the specific resistanceof the target was 0.002 Ωcm to 6 Ωcm.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. The sputtering conditionswere, as shown in Table 3: DC sputtering was performed in an Ar gasatmosphere or Ar gas-O₂ (20%) gas atmosphere and at a gas pressure of0.5 Pa, gas flow rate of 50 sccm, and sputtering power of 500 to 1000 w.A 1 μm sputtered film was formed on the glass substrate. The depositionrate and composition of the film analyzed with EPMA are respectivelyshown in Table 3. As Table 3 shows, O/(2Ti+Co) was 0.84 to 0.94. Therefractive index and extinction coefficient of the sputtered film weremeasured. They were measured with an ellipsometer using a lightwavelength of 405 nm. The results are similarly shown in Table 3.

As a result of the above, Comparative Example 8 did not satisfy theconditions of the present invention since the ratio of oxygen componentto metal components, O/(2Ti+Co) was 0.94. Here, the refractive index waslow at 2.57, and the extinction coefficient also increased to 0.11.Thus, it was inadequate as an interference film or a protective film ofan optical recording medium. Comparative Example 9 did not satisfy theconditions of the present invention since the Co amount was too great at12.5 at % and the ratio of oxygen component to metal components,O/(2Ti+Co) was 0.84. Here, the refractive index was low at 2.55, and theextinction coefficient increased to 0.32. Thus, it was inadequate as aninterference film or a protective film of an optical recording medium.

Example 22 to Example 26

As the raw materials, titanium oxide (TiO₂) with an average particlediameter of 1 μm and purity of 4N (99.99%), and platinum (Pt) powderwith an average particle diameter of 7 μm and purity of 3N (99.9%) wereused. These were blended and mixed to achieve the target compositionsshown in Table 4. One kg of this mixed powder was mixed using a wet ballmill so that Pt is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried by vaporizing moisture wasfilled in a carbon die and hot pressed. The hot press conditions were1000° C., and bearing of 250 kgf/cm². The obtained sintered compact wasmachined to obtain a target of φ152 mm and 5 mmt. Consequently, targetswith density of 95% or higher and specific resistance of 0.07 to 50 Ωcmas shown in Table 4 were obtained.

TABLE 4 Film Composition Specific Deposition Composition of TargetResistance Sputter Speed Ti Pt O O/(2Ti + Refractive Extinction (at %)(Ωcm) gas (Å/sec/kW) (at %) (at %) (at %) Pt) index coefficient Example22 TiO₂:Pt = 85:15 1 Ar—10%O₂ 0.5 30.9 5.5 63.6 0.95 2.74 0.1 Example 23TiO₂:Pt = 95:5 50 Ar—2%O₂ 1.4 32.8 1.7 65.5 0.97 2.70 0.05 Example 24TiO₂:Pt = 99:1 6 Ar—2%O₂ 1.3 33.2 0.4 66.4 0.99 2.65 0.02 Example 25TiO₂:Pt = 99.9:0.1 10 Ar 2 33.2 0.04 66.76 1.00 2.64 0.01 Example 26TiO_(1.9):Pt = 99.99:0.01 0.07 Ar—1%O₂ 1.4 33.3 0.004 66.696 1.00 2.620.008 Comparative TiO₂:Pt = 95:5 50 Ar 2.3 34 1.8 64.2 0.92 2.69 0.21Example 10 Comparative TiO₂:Pt = 80:20 0.005 Ar—20%O₂ 0.4 30.8 7.7 61.50.89 2.65 0.4 Example 11

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. The sputtering conditionswere, as shown in Table 4: DC sputtering was performed in an Ar gasatmosphere or Ar gas-O₂ (1 to 10%) gas atmosphere and at a gas pressureof 0.5 Pa, gas flow rate of 50 sccm, and sputtering power of 500 to 1000w. Thus, it was possible to perform DC sputtering without any problem,and it was confirmed that the target possesses conductivity. A 1 μmsputtered film was formed on the glass substrate. The deposition rateand composition of the film analyzed with EPMA are respectively shown inTable 4. As Table 4 shows, O/(2Ti+Pt) was 0.95 to 1.00. The refractiveindex and extinction coefficient of the sputtered film were measured.They were measured with an ellipsometer using a light wavelength of 405nm. The results are similarly shown in Table 4. Consequently, therefractive index was high at 2.62 to 2.74, and the extinctioncoefficient decreased at 0.008 to 0.1. In all cases it was possible toform an interference film or a protective film suitable for an opticalrecording medium.

Comparative Example 10 and Comparative Example 11

As the raw materials, titanium oxide (TiO₂) with an average particlediameter of 1 μm and purity of 4N (99.99%), and platinum (Pt) powderwith an average particle diameter of 7 μm and purity of 3N (99.9%) wereused. These were blended and mixed to achieve the target compositionsshown in Table 4. One kg of this mixed powder was mixed using a wet ballmill so that Pt is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried by vaporizing moisture wasfilled in a carbon die and hot pressed. The hot press conditions were1000° C., and bearing of 250 kgf/cm². The obtained sintered compact wasmachined to obtain a target of φ152 mm and 5 mmt. Consequently, thedensity was 95% or higher. As shown in Table 4, the specific resistanceof the target was 0.005 Ωcm to 50 Ωcm.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. The sputtering conditionswere, as shown in Table 4: DC sputtering was performed in an Ar gasatmosphere or Ar gas-O₂ (20%) gas atmosphere and at a gas pressure of0.5 Pa, gas flow rate of 50 sccm, and sputtering power of 500 to 1000 w.A 1 μm sputtered film was formed on the glass substrate. The depositionrate and composition of the film analyzed with EPMA are respectivelyshown in Table 4. As Table 4 shows, O/(2Ti+Pt) was 0.89 to 0.92. Therefractive index and extinction coefficient of the sputtered film weremeasured. They were measured with an ellipsometer using a lightwavelength of 405 nm. The results are similarly shown in Table 4.

As a result of the above, Comparative Example 10 did not satisfy theconditions of the present invention since the ratio of oxygen componentto metal components, O/(2Ti+Pt) was 0.92. Here, although the refractiveindex was high at 2.69, the extinction coefficient increased to 0.21.Thus, it was inadequate as an interference film or a protective film ofan optical recording medium. Comparative Example 11 did not satisfy theconditions of the present invention since the Pt amount was too great at7.7 at % and the ratio of oxygen component to metal components,O/(2Ti+Pt) was 0.89. Here, although the refractive index was high at2.65, the extinction coefficient increased to 0.4. Thus, it wasinadequate as an interference film or a protective film of an opticalrecording medium.

Example 27 to Example 32

As the raw materials, titanium oxide (TiO₂) with an average particlediameter of 1 μm and purity of 4N (99.99%), and nickel (Ni) powder withan average particle diameter of 20 μm and purity of 3N (99.9%) wereused. These were blended and mixed to achieve the target compositionsshown in Table 5. One kg of this mixed powder was mixed using a wet ballmill so that Ni is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried by vaporizing moisture wasfilled in a carbon die and hot pressed. The hot press conditions were1000° C., and bearing of 250 kgf/cm². The obtained sintered compact wasmachined to obtain a target of φ152 mm and 5 mmt. Consequently, targetswith density of 95% or higher and specific resistance of 0.06 to 37 Ωcmas shown in Table 5 were obtained.

TABLE 5 Film Composition Specific Deposition Composition of TargetResistance Sputter Speed Ti Ni O O/(2Ti + Refractive Extinction (at %)(Ωcm) gas (Å/sec/kW) (at %) (at %) (at %) Ni) index coefficient Example27 TiO₂:Ni = 90:10 11 Ar—4%O₂ 0.6 31.9 3.5 64.6 0.96 2.65 0.08 Example28 TiO₂:Ni = 95:5 22 Ar—2%O₂ 0.9 32.8 1.8 65.4 0.97 2.63 0.04 Example 29TiO₂:Ni = 99:1 37 Ar—2%O₂ 0.8 33.2 0.4 66.4 0.99 2.62 0.01 Example 30TiO₂:Ni = 99.9:0.1 8 Ar 1.6 33.3 0.04 66.66 1.00 2.61 0.008 Example 31TiO₂:Ni = 80:20 0.2 Ar—10%O₂ 0.4 29.5 7.2 63.3 0.96 2.68 0.1 Example 32TiO_(1.9):Ni = 99.99:0.01 0.06 Ar—0.5%O₂ 1.3 33.5 0.004 66.496 0.99 2.660.02 Comparative TiO₂:Ni = 90:10 11 Ar 1.8 32.3 3.8 63.9 0.93 2.58 0.15Example 12 Comparative TiO₂:Ni = 70:30 0.005 Ar—20%O₂ 0.3 28.9 12.5 58.60.83 2.54 0.35 Example 13

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. The sputtering conditionswere, as shown in Table 5: DC sputtering was performed in an Ar gasatmosphere or Ar gas-O₂ (0.5 to 10%) gas atmosphere and at a gaspressure of 0.5 Pa, gas flow rate of 50 sccm, and sputtering power of500 to 1000 w. Thus, it was possible to perform DC sputtering withoutany problem, and it was confirmed that the target possessesconductivity. A 1 μm sputtered film was formed on the glass substrate.The deposition rate and composition of the film analyzed with EPMA arerespectively shown in Table 5. As Table 5 shows, O/(2Ti+Ni) was 0.96 to1.00. The refractive index and extinction coefficient of the sputteredfilm were measured. They were measured with an ellipsometer using alight wavelength of 405 nm. The results are similarly shown in Table 5.Consequently, the refractive index was high at 2.61 to 2.68, and theextinction coefficient decreased at 0.008 to 0.1. In all cases it waspossible to form an interference film or a protective film suitable foran optical recording medium.

Comparative Example 12 and Comparative Example 13

As the raw materials, titanium oxide (TiO₂) with an average particlediameter of 1 μm and purity of 4N (99.99%), and nickel (Ni) powder withan average particle diameter of 7 μm and purity of 3N (99.9%) were used.These were blended and mixed to achieve the target compositions shown inTable 5. One kg of this mixed powder was mixed using a wet ball mill sothat Ni is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried by vaporizing moisture wasfilled in a carbon die and hot pressed. The hot press conditions were1000° C., and bearing of 250 kgf/cm². The obtained sintered compact wasmachined to obtain a target of φ152 mm and 5 mmt. Consequently, thedensity was 95% or higher. As shown in Table 5, the specific resistanceof the target was 0.005 Ωcm to 11 Ωcm.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. The sputtering conditionswere, as shown in Table 5: DC sputtering was performed in an Ar gasatmosphere or Ar gas-O₂ (20%) gas atmosphere and at a gas pressure of0.5 Pa, gas flow rate of 50 sccm, and sputtering power of 500 to 1000 w.A 1 μm sputtered film was formed on the glass substrate. The depositionrate and composition of the film analyzed with EPMA are respectivelyshown in Table 5. As Table 5 shows, O/(2Ti+Ni) was 0.83 to 0.93. Therefractive index and extinction coefficient of the sputtered film weremeasured. They were measured with an ellipsometer using a lightwavelength of 405 nm. The results are similarly shown in Table 5.

As a result of the above, Comparative Example 12 did not satisfy theconditions of the present invention since the ratio of oxygen componentto metal components, O/(2Ti+Ni) was 0.93. Here, the refractive index waslow at 2.58, and the extinction coefficient increased to 0.15. Thus, itwas inadequate as an interference film or a protective film of anoptical recording medium. Comparative Example 13 did not satisfy theconditions of the present invention since the Ni amount was too great at12.5 at % and the ratio of oxygen component to metal components,O/(2Ti+Ni) was 0.83. Here, the refractive index was low at 2.54, and theextinction coefficient increased to 0.35. Thus, it was inadequate as aninterference film or a protective film of an optical recording medium.

Example 33 to Example 38

As the raw materials, titanium oxide (TiO₂) with an average particlediameter of 3 μm and purity of 4N (99.99%), and gold (Au) powder with anaverage particle diameter of 20 μm and purity of 3N (99.9%) were used.These were blended and mixed to achieve the target compositions shown inTable 6. One kg of this mixed powder was mixed using a wet ball mill sothat Au is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried by vaporizing moisture wasfilled in a carbon die and hot pressed. The hot press conditions were950° C., and bearing of 350 kgf/cm². The obtained sintered compact wasmachined to obtain a target of φ152 mm and 5 mmt. Consequently, targetswith density of 95% or higher and specific resistance of 0.06 to 51 Ωcmas shown in Table 6 were obtained.

TABLE 6 Film Composition Specific Deposition Resistance Sputter Speed TiAu O O/(2Ti + Refractive Extinction Composition of Target (Ωcm) gas(Å/sec/kW) (at %) (at %) (at %) Au) index coefficient Example 33 TiO₂:Au= 90:10 18 Ar—4%O₂ 0.8 31.9 3.6 64.5 0.96 2.69 0.09 Example 34 TiO₂:Au =95:5 35 Ar—2%O₂ 1 32.8 1.7 65.5 0.97 2.66 0.06 Example 35 TiO₂:Au = 99:151 Ar—2%O₂ 0.8 33.2 0.4 66.4 0.99 2.64 0.02 Example 36 TiO₂:Au =99.9:0.1 7 Ar 1.5 33.3 0.04 66.66 1.00 2.62 0.007 Example 37 TiO₂:Au =80:20 0.6 Ar—10%O₂ 0.4 29.3 7.5 63.2 0.96 2.70 0.1 Example 38TiO_(1.9):Au = 99.99:0.01 0.06 Ar—0.5%O₂ 1.5 33.4 0.004 66.596 1.00 2.650.01 Comparative TiO₂:Au = 95:5 35 Ar 1.9 34 1.8 64.2 0.92 2.60 0.13Example 14 Comparative TiO₂:Au = 70:30 0.01 Ar—20%O₂ 0.3 29.1 12.5 58.40.83 2.56 0.32 Example 15

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. The sputtering conditionswere, as shown in Table 6: DC sputtering was performed in an Ar gasatmosphere or Ar gas-O₂ (0.5 to 10%) gas atmosphere and at a gaspressure of 0.5 Pa, gas flow rate of 50 scan, and sputtering power of500 to 1000 w. Thus, it was possible to perform DC sputtering withoutany problem, and was confirmed that the target possesses conductivity. A1 μm sputtered film was formed on the glass substrate. The depositionrate and composition of the film analyzed with EPMA are respectivelyshown in Table 6. As Table 6 shows, O/(2Ti+Au) was 0.96 to 1.00. Therefractive index and extinction coefficient of the sputtered film weremeasured. The measurement was carried out with an ellipsometer using alight wavelength of 405 nm. The results are similarly shown in Table 6.Consequently, the refractive index was high at 2.62 to 2.70, and theextinction coefficient decreased at 0.007 to 0.1. In all cases it waspossible to form an interference film or a protective film suitable foran optical recording medium.

Comparative Example 14 and Comparative Example 15

As the raw materials, titanium oxide (TiO₂) with an average particlediameter of 3 μm and purity of 4N (99.99%), and gold (Au) powder with anaverage particle diameter of 20 μm and purity of 3N (99.9%) were used.These were blended and mixed to achieve the target compositions shown inTable 6. One kg of this mixed powder was mixed using a wet ball mill sothat Au is uniformly dispersed in the titanium oxide powder.Subsequently, the mixed powder that was dried by vaporizing moisture wasfilled in a carbon die and hot pressed. The hot press conditions were950° C., and bearing of 350 kgf/cm². The particle size of the rawmaterials, hot press conditions, bearing, and particle size of the Auphase in the target of Comparative Example 14 and Comparative Example 15are similarly shown in Table 6. The obtained sintered compact wasmachined to obtain a target of φ152 mm and 5 mmt. Consequently, thedensity was 95% or higher. As shown in Table 6, the specific resistanceof the target was 0.01 Ωcm to 35 Ωcm.

Subsequently, the sputtering target produced as described above was usedto form a sputtered film on a glass substrate. The sputtering conditionswere, as shown in Table 6: DC sputtering was performed in an Ar gasatmosphere or Ar gas-O² (20%) gas atmosphere and at a gas pressure of0.5 Pa, gas flow rate of 50 sccm, and sputtering power of 500 to 1000 w.A 1 μm sputtered film was formed on the glass substrate. The depositionrate and composition of the film analyzed with EPMA are respectivelyshown in Table 6. As Table 6 shows, O/(2Ti+Au) was 0.83 to 0.92. Therefractive index and extinction coefficient of the sputtered film weremeasured. They were measured with an ellipsometer using a lightwavelength of 405 nm. The results are similarly shown in Table 6.

As a result of the above, Comparative Example 14 did not satisfy theconditions of the present invention since the ratio of oxygen componentto metal components, O/(2Ti+Au) was 0.92. Here, although the refractiveindex was high at 2.60, the extinction coefficient increased to 0.13.Thus, it was inadequate as an interference film or a protective film ofan optical recording medium. Comparative Example 15 did not satisfy theconditions of the present invention since the Au amount was too great at12.5 at % and the ratio of oxygen component to metal components,O/(2Ti+Au) was 0.83. Here, the refractive index was low at 2.56, and theextinction coefficient increased to 0.32. Thus, it was inadequate as aninterference film or a protective film of an optical recording medium.

SUMMARY OF EXAMPLES AND COMPARATIVE EXAMPLES

Among the foregoing Examples and Comparative Examples, those within thescope of the present invention all had a high refractive index and lowextinction coefficient. Similarly, with respect to those in which therespective components of the sputtering target satisfied the conditionsof the present invention, the specific resistance of the target was 100Ωcm or less in all cases, and favorable results were yielded in that anabnormal discharge could not be observed.

This invention provides a thin film comprising titanium oxide as itsmain component with a high refractive index and low extinctioncoefficient and a sintered compact sputtering target comprising titaniumoxide as its main component which is suitable for producing theforegoing thin film, and the thin film obtained with the presentinvention can be used as a film or layer of an optical informationrecording medium of electronic parts such as CDs and DVDs. Moreover, thethin film of the present invention yields superior transmittance and lowreflectance and is particularly effective as an interference film orprotective film of an optical information recording medium. A highmelting point dielectric protective layer has tolerance against repeatedthermal stress by warming and cooling, and is effective as a dielectricprotective layer in which the foregoing thermal effect does not affectthe reflective film or other locations, which itself is thin, has lowreflectance, and which requires strength that is free fromdeterioration. In addition, a material possessing the foregoingcharacteristics can be applied to architectural glass, glass forautomobiles, CRT, and flat displays; that is, it can be used as a heatray reflective film, antireflection film, and interference filter.

1. An optical interference film or a protective film of an opticalinformation recording medium which is formed by performing DC sputteringto a target comprising titanium oxide as its main component, wherein thefilm includes titanium, oxygen and platinum, content of Ti is 29.0% orhigher and 34.0 at % or less and content of Pt is 0.003 at % or higherand 5.7 at % or less with the remainder being oxygen and unavoidableimpurities, and ratio of oxygen component to metal components,O/(2Ti+Pt), is 0.95 or higher.
 2. The film according to claim 1, whereina refractive index of the film in a wavelength region of 400 to 410 nmis 2.60 or higher.
 3. The film according to claim 2, wherein anextinction coefficient of the film in a wavelength region of 400 to 410nm is 0.1 or less.
 4. The film according to claim 3, wherein theextinction coefficient in the wavelength region of 400 to 410 nm is 0.05or less.
 5. The film according to claim 1, wherein an extinctioncoefficient of the film in a wavelength region of 400 to 410 nm is 0.1or less.
 6. The film according to claim 1, wherein an extinctioncoefficient of the film in a wavelength region of 400 to 410 nm is 0.05or less.
 7. A sintered compact target for DC sputtering for forming anoptical interference film or a protective film of an optical informationrecording medium comprising titanium oxide as its main component,wherein the target includes platinum and comprises, as its maincomponent, titanium oxide made of titanium, oxygen and unavoidableimpurities as a remainder thereof, the respective components have acomposition ratio of (TiO_(2-m))_(1-n)Pt_(n) provided that 0≦m≦0.5 and0.0001≦n≦0.15, and the target has a specific resistance of 100 Ωcm orless.